An inventory model for multiple items assuming time-varying demands and limited storage

Producción CientíficaA model for inventory systems with multiple products is studied. Demands of items are time-dependent and follow power patterns. Shortages are allowed and fully back logged. For this inventory system, our findings provide the efficient inventory policy that helps decision-makers to obtain the initial inventory levels and the reorder points that maximize the profit per unit time. Moreover, when it is assumed that the warehouse used for the storage of products has a limited capacity, the optimal inventory policy is also developed. The model presented here extends some inventory systems studied by other authors. Numerical examples are introduced to illustrate the applicability of the theoretical results presented.Ministerio de Ciencia, Innovación y Universidades cofinanciado por la Comunidad Europea (FEDER) (project MTM2017-84150-P)Publicación en abierto financiada por el Consorcio de Bibliotecas Universitarias de Castilla y León (BUCLE), con cargo al Programa Operativo 2014ES16RFOP009 FEDER 2014-2020 DE CASTILLA Y LEÓN, Actuación:20007-CL - Apoyo Consorcio BUCL

Optimal price and lot size for an EOQ model with full backordering under power price and time dependent demand

Producción CientíficaIn this paper, we address an inventory system where the demand rate multiplicatively combines the effects of time and selling price. It is assumed that the demand rate is the product of two power functions, one depending on the selling price and the other on the time elapsed since the last inventory replenishment. Shortages are allowed and fully backlogged. The aim is to obtain the lot sizing, the inventory cycle and the unit selling price that maximize the profit per unit time. To achieve this, two efficient algorithms are proposed to obtain the optimal solution to the inventory problem for all possible parameter values of the system. We solve several numerical examples to illustrate the theoretical results and the solution methodology. We also develop a numerical sensitivity analysis of the optimal inventory policy and the maximum profit with respect to the parameters of the demand function.Ministerio de Ciencia, Innovación y Universidades y Fondo Europeo de Desarrollo Regional (FEDER) - (Project MTM2017-84150-P

Caracterización del banco de semillas de cuatro agroecosistemas de la Frailesca, Chiapas, México

The objective of the study was to determine the dynamics of weeds of the seed bank in the representative agro-ecosystems of the tropical region of Frailesca, in the state of Chiapas, Mexico. The systems studied were: the fertile soils (river banks), paddock (grasslands), intermediate lands for the cultivation of corn and in secondary succession (acahual). The methodology of weed characterization consisted on direct seed germination of seed of weed from three soil layers: 0-10, 10-20 and 20-30 cm. Soil samples from these soil layers were placed in trays of 50 x 30 x 10 cm. Each system and soil layer were replicated three times with a total of 36 total sampling units (trays). Trays were placed in a greenhouse and contamination with other seeds was avoided. The variables evaluated were the number of emerged weed species and the number of individuals per weed species, density and relative dominance, floristic diversity and community similarities, and allelopathic effects of the dominant weeds. The results indicate that the intensively managed systems with agricultural activities specifically in fertile and intermediate lands for corn monoculture presented more dynamic seed banks, which occurred in the first 10 cm depth of the soil. The dominant weed species were Cyperus rotundus L. and Melampodium divaricatum Rich. Floristic diversity determined similar indices between systems and depths. The greatest similarities between communities was found among the agroecosystems managed at corn cultivation. No allelopathic effects of the dominant species on the germination and growth of the representative crops in the region were determined.El objetivo del trabajo fue caracterizar las arvenses del banco de semillas de agroecosistemas representativos de la región tropical denominada Frailesca, en el estado de Chiapas, México. Los sistemas definidos estuvieron representados por los suelos de vega (márgenes de los ríos), potreros (pastizales), terrenos intermedios para el cultivo de maíz y en sucesión secundaria (acahual). La metodología se fundamentó en la germinación directa, para lo cual se obtuvieron muestras compuestas de suelo a tres profundidades (0-10, 10-20 y 20-30 cm), las cuales se colocaron en charolas de 50 x 30 x 10 cm, ubicándolas en invernadero para evitar su contaminación, proporcionándoles riegos regulares. Cada sistema estuvo representado por tres réplicas, 36 unidades de muestreo totales. Las variables evaluadas fueron número de especies e individuos emergidos, densidad y dominancia relativa, diversidad florística y similitud de comunidades y efectos alelopáticos de las arvenses dominantes. Los resultados indican que los sistemas manejados intensivamente para actividades agrícolas, específicamente terrenos de vega e intermedios para el monocultivo de maíz, presentaron bancos de semillas más dinámicos, lo cual sucede en los primeros 10 cm de profundidad. Las especies de arvenses dominantes de los bancos evaluados fueron Cyperus rotundus L. y Melampodium divaricatum Rich. La diversidad florística determinó índices similares entre los sistemas y profundidades. La mayor similitud entre comunidades se presentó en los agroecosistemas manejados con el cultivo maíz. No se determinaron efectos alelopáticos de las especies dominantes sobre la germinación y crecimiento de los cultivos representativos de la región

Métodos y técnicas de monitoreo y predicción temprana en los escenarios de riesgos socionaturales

Esta obra concentra los métodos y las técnicas fundamentales para el seguimiento y monitoreo de las dinámicas de los escenarios de riesgos socionaturales (geológicos e hidrometeorológicos) y tiene como objetivo general orientar, apoyar y acompañar a los directivos y operativos de protección civil en aterrizar las acciones y políticas públicas enfocadas a la gestión del riesgo local de desastre

Profit maximization in an inventory system with time-varying demand, partial backordering and discrete inventory cycle

Producción CientíficaIn this paper, an inventory problem where the inventory cycle must be an integer multiple of a known basic period is considered. Furthermore, the demand rate in each basic period is a power time-dependent function. Shortages are allowed but, taking necessities or interests of the customers into account, only a fixed proportion of the demand during the stock-out period is satisfied with the arrival of the next replenishment. The costs related to the management of the inventory system are the ordering cost, the purchasing cost, the holding cost, the backordering cost and the lost sale cost. The problem is to determine the best inventory policy that maximizes the profit per unit time, which is the difference between the income obtained from the sales of the product and the sum of the previous costs. The modeling of the inventory problem leads to an integer nonlinear mathematical programming problem. To solve this problem, a new and efficient algorithm to calculate the optimal inventory cycle and the economic order quantity is proposed. Numerical examples are presented to illustrate how the algorithm works to determine the best inventory policies. A sensitivity analysis of the optimal policy with respect to some parameters of the inventory system is developed. Finally, conclusions and suggestions for future research lines are given.Ministerio de Economía, Industria y Competitividad y fondos europeos FEDER (research project MTM2017-84150-P

Caracterización del banco de semillas de cuatro agroecosistemas de la Frailesca, Chiapas, México

The objective of the study was to determine the dynamics of weeds of the seed bank in the representative agro-ecosystems of the tropical region of Frailesca, in the state of Chiapas, Mexico. The systems studied were: the fertile soils (river banks), paddock (grasslands), intermediate lands for the cultivation of corn and in secondary succession (acahual). The methodology of weed characterization consisted on direct seed germination of seed of weed from three soil layers: 0-10, 10-20 and 20-30 cm. Soil samples from these soil layers were placed in trays of 50 x 30 x 10 cm. Each system and soil layer were replicated three times with a total of 36 total sampling units (trays). Trays were placed in a greenhouse and contamination with other seeds was avoided. The variables evaluated were the number of emerged weed species and the number of individuals per weed species, density and relative dominance, floristic diversity and community similarities, and allelopathic effects of the dominant weeds. The results indicate that the intensively managed systems with agricultural activities specifically in fertile and intermediate lands for corn monoculture presented more dynamic seed banks, which occurred in the first 10 cm depth of the soil. The dominant weed species were Cyperus rotundus L. and Melampodium divaricatum Rich. Floristic diversity determined similar indices between systems and depths. The greatest similarities between communities was found among the agroecosystems managed at corn cultivation. No allelopathic effects of the dominant species on the germination and growth of the representative crops in the region were determined.El objetivo del trabajo fue caracterizar las arvenses del banco de semillas de agroecosistemas representativos de la región tropical denominada Frailesca, en el estado de Chiapas, México. Los sistemas definidos estuvieron representados por los suelos de vega (márgenes de los ríos), potreros (pastizales), terrenos intermedios para el cultivo de maíz y en sucesión secundaria (acahual). La metodología se fundamentó en la germinación directa, para lo cual se obtuvieron muestras compuestas de suelo a tres profundidades (0-10, 10-20 y 20-30 cm), las cuales se colocaron en charolas de 50 x 30 x 10 cm, ubicándolas en invernadero para evitar su contaminación, proporcionándoles riegos regulares. Cada sistema estuvo representado por tres réplicas, 36 unidades de muestreo totales. Las variables evaluadas fueron número de especies e individuos emergidos, densidad y dominancia relativa, diversidad florística y similitud de comunidades y efectos alelopáticos de las arvenses dominantes. Los resultados indican que los sistemas manejados intensivamente para actividades agrícolas, específicamente terrenos de vega e intermedios para el monocultivo de maíz, presentaron bancos de semillas más dinámicos, lo cual sucede en los primeros 10 cm de profundidad. Las especies de arvenses dominantes de los bancos evaluados fueron Cyperus rotundus L. y Melampodium divaricatum Rich. La diversidad florística determinó índices similares entre los sistemas y profundidades. La mayor similitud entre comunidades se presentó en los agroecosistemas manejados con el cultivo maíz. No se determinaron efectos alelopáticos de las especies dominantes sobre la germinación y crecimiento de los cultivos representativos de la región

Culture alternation, effect on soil in tobacco zones of Pinar del Río province

The tobacco constitutes an important source of income to the Pinar del Río province. However, production technologies have contributed to the degradation of soils; crop alternating is one of the effective measures to mitigate this effect. The objective of the investigation was to evaluate the incidence of different variants of alternation in some chemical and physic - chemical properties of the soil. The work was developed in areas dedicated to the tobacco crop, the variants of alternation evaluated were uncultivated soil, tobacco - fallow, tobacco - corn and tobacco - polycultures. In the selected areas, 96 samples were collected at depths of 20 cm and 40 cm and 40 producers were surveyed. Descriptive statistical methods were applied to compare the means in each variant of land use. The results showed that the predominant pH was slightly acidic, the tobacco-fallow variant showed values close to neutrality. The content of organic matter did not exceed 1% in the variants of cultivated soils inferior to those not cultivated, changeable bases and cation exchange capacity were similar in the cultivated soils, and the calcium showed the highest values in tobacco-fallow. It is concluded that the different land use variants did not have a marked effect on the pH values. The content of soluble phosphorus increased in all the variants of cultivated soils. The alternation of crops, as the only measure of improvement, does not guarantee an improvement in the chemical and physic - chemical properties of the soils

La Libreta

Comunicación presentada en las Jornadas sobre Investigación e Innovación en la Educación Física escolar celebradas en el CEP de La Laguna, del 2 al 5 de junio de 2010Se presenta una actividad que trata de lograr que el alumnado tome decisiones en la preparación y organización de las tareas de clase de Educación Física. Se ha utilizado el “Grupo Estrella” como estrategia metodológica para favorecer la autonomía del alumnado. Del análisis de los resultados se desprende que una docencia donde se le deje tomar responsabilidades a los alumnos y alumnas proporciona satisfacción respecto al área, no obstante, la percepción del alumnado es que se pierde más tiempo y se aprende menos. La intervención docente debería ir encaminada a solventar estas percepciones.ES

Patients with Crohn's disease have longer post-operative in-hospital stay than patients with colon cancer but no difference in complications' rate

BACKGROUNDRight hemicolectomy or ileocecal resection are used to treat benign conditions like Crohn's disease (CD) and malignant ones like colon cancer (CC).AIMTo investigate differences in pre- and peri-operative factors and their impact on post-operative outcome in patients with CC and CD.METHODSThis is a sub-group analysis of the European Society of Coloproctology's prospective, multi-centre snapshot audit. Adult patients with CC and CD undergoing right hemicolectomy or ileocecal resection were included. Primary outcome measure was 30-d post-operative complications. Secondary outcome measures were post-operative length of stay (LOS) at and readmission.RESULTSThree hundred and seventy-five patients with CD and 2,515 patients with CC were included. Patients with CD were younger (median = 37 years for CD and 71 years for CC (P < 0.01), had lower American Society of Anesthesiology score (ASA) grade (P < 0.01) and less comorbidity (P < 0.01), but were more likely to be current smokers (P < 0.01). Patients with CD were more frequently operated on by colorectal surgeons (P < 0.01) and frequently underwent ileocecal resection (P < 0.01) with higher rate of de-functioning/primary stoma construction (P < 0.01). Thirty-day post-operative mortality occurred exclusively in the CC group (66/2515, 2.3%). In multivariate analyses, the risk of post-operative complications was similar in the two groups (OR 0.80, 95%CI: 0.54-1.17; P = 0.25). Patients with CD had a significantly longer LOS (Geometric mean 0.87, 95%CI: 0.79-0.95; P < 0.01). There was no difference in re-admission rates. The audit did not collect data on post-operative enhanced recovery protocols that are implemented in the different participating centers.CONCLUSIONPatients with CD were younger, with lower ASA grade, less comorbidity, operated on by experienced surgeons and underwent less radical resection but had a longer LOS than patients with CC although complication's rate was not different between the two groups